Joint Biomechanics — MCQs
Identify the type of joint in the image provided.
In walking, gravity tends to tilt pelvis and trunk to the unsupported side, the major factor in preventing this unwanted movement is?
The image shows a highlighted region on the dorsal aspect of the hand (anatomical snuffbox). Which of the following anatomical structures form the boundaries or floor of this region?
All of the following are examples of traction epiphysis except which of the following?
Hilton's law primarily relates to which of the following?
A moving vehicle hits a pedestrian on his lateral aspect of the knee and causes a fracture. The fracture line is passing through the intercondylar eminence. Which of the following structures will most likely be injured
The mechanoreceptors in joints and ligaments are:
Which muscles are paralyzed if there is hyperextension of metacarpophalangeal joint and flexion of the interphalangeal joint?
In Articular cartilage, most active chondrocytes are seen in ?
A sportsman presented to you after injury during practice exercise. You performed the test given in the image, and it came out as positive. What is the diagnosis?
Joint Biomechanics Indian Medical PG Practice Questions and MCQs
Question 1: Identify the type of joint in the image provided.
- A. Syndesmosis
- B. Synarthrosis
- C. Synovial joint (Correct Answer)
- D. Symphysis
Explanation: ***Synovial joint*** - The image depicts a **costovertebral joint**, which connects a rib to a thoracic vertebra. These joints are **diarthrotic**, meaning they are freely movable, characteristic of synovial joints. - Synovial joints are characterized by the presence of a **synovial cavity**, articular cartilage, an articular capsule, and synovial fluid, allowing for a wide range of motion. *Syndesmosis* - A syndesmosis is a type of **fibrous joint** where two bones are joined by a ligament or a membrane, allowing for very limited movement, such as the distal tibiofibular joint. - This definition does not match the image, which shows a joint designed for movement between the rib and vertebra. *Synarthrosis* - Synarthrosis is a classification for **immovable joints**, such as sutures in the skull. - The costovertebral joints, as shown, allow for movement during respiration and are therefore not synarthrotic. *Symphysis* - A symphysis is a type of **cartilaginous joint** where bones are joined by **fibrocartilage**, allowing for slight movement. Examples include the pubic symphysis or intervertebral discs. - The costovertebral joint shown in the image is a synovial articulation, not a cartilaginous joint.
Question 2: In walking, gravity tends to tilt pelvis and trunk to the unsupported side, the major factor in preventing this unwanted movement is?
- A. Adductor muscles
- B. Quadriceps
- C. Gluteus medius and minimus (Correct Answer)
- D. Gluteus maximus
Explanation: ***Gluteus medius and minimus*** - The **gluteus medius** and **gluteus minimus** are essential **abductors** of the hip, primarily responsible for stabilizing the pelvis during the **single-limb support phase of gait**. - When one leg is lifted during walking, these muscles on the **stance leg side** contract to prevent the pelvis from tilting downwards on the unsupported swing leg side. *Adductor muscles* - **Adductor muscles** (adductor longus, brevis, magnus, pectineus, gracilis) primarily function to bring the thigh toward the midline of the body. - While they play a role in gait stability, their main action is not to prevent the lateral pelvic tilt described. *Quadriceps* - The quadriceps femoris group (rectus femoris, vastus lateralis, medialis, intermedius) are powerful **extensors of the knee**. - They are crucial for weight acceptance and propulsion during walking but do not directly prevent lateral pelvic tilt [1]. *Gluteus maximus* - The **gluteus maximus** is the largest and most powerful muscle of the hip, primarily responsible for **hip extension** and **external rotation**. - It is crucial for activities like climbing stairs or running, but its main role in normal walking is not to prevent lateral pelvic tilt; that function is more specific to the gluteus medius and minimus.
Question 3: The image shows a highlighted region on the dorsal aspect of the hand (anatomical snuffbox). Which of the following anatomical structures form the boundaries or floor of this region?
- A. Abductor pollicis longus muscle.
- B. Styloid process of the radius.
- C. Extensor pollicis longus muscle.
- D. All of the above anatomical structures. (Correct Answer)
Explanation: ***All of the above anatomical structures.*** - The image highlights the **anatomical snuffbox**, a triangular depression on the radial dorsal aspect of the hand. Its boundaries are formed by the tendons of the **extensor pollicis longus muscle** (ulnar side), and the **abductor pollicis longus** and **extensor pollicis brevis muscles** (radial side). - The **styloid process of the radius** forms the floor of the anatomical snuffbox along with the scaphoid and trapezium bones. All the options listed are key anatomical features associated with this region. *Extensor pollicis longus muscle.* - This muscle forms the **ulnar (medial) border** of the anatomical snuffbox. - Its tendon can be palpated during **thumb extension** and contributes to the overall structure of the highlighted area. *Abductor pollicis longus muscle.* - This muscle, along with the extensor pollicis brevis, forms the **radial (lateral) border** of the anatomical snuffbox. - Its tendon is visible and palpable on the radial side of the highlighted region when the thumb is abducted. *Styloid process of the radius.* - This bony prominence is located at the **distal end of the radius** on the radial side of the wrist. - It forms part of the **proximal floor** of the anatomical snuffbox, contributing to its definition.
Question 4: All of the following are examples of traction epiphysis except which of the following?
- A. Tubercles of humerus.
- B. Posterior tubercle of talus. (Correct Answer)
- C. Trochanters of femur.
- D. Tibial tuberosity.
Explanation: ***Posterior tubercle of talus*** - The posterior tubercle of the **talus** is not typically considered a traction epiphysis because it's an integral part of the talar body, involved in joint articulation rather than being a site of significant muscle or ligament attachment pulling on a separate ossification center. - While the **flexor hallucis longus** tendon grooves its surface, its primary function and development are not driven by the tensile forces characteristic of traction epiphyses. *Tubercles of humerus* - The **greater and lesser tubercles of the humerus** are classic examples of **traction epiphyses**. - They serve as insertion sites for the **rotator cuff muscles** (supraspinatus, infraspinatus, teres minor, and subscapularis), where strong repetitive pulling forces stimulate their development. *Trochanters of femur* - The **greater and lesser trochanters of the femur** are well-known examples of **traction epiphyses**. - They provide points of attachment for powerful hip and thigh muscles, such as the **gluteal muscles** (greater trochanter) and **iliopsoas** (lesser trochanter), which exert significant traction forces during growth. *Tibial tuberosity* - The **tibial tuberosity** is a prominent example of a **traction epiphysis**. - It serves as the insertion point for the **patellar ligament**, transmitting the force of the **quadriceps femoris** muscle, making it subject to repetitive traction during growth and development.
Question 5: Hilton's law primarily relates to which of the following?
- A. Nerve innervation only
- B. Nerve supply of joints, muscles moving them, and overlying skin (Correct Answer)
- C. Blood supply to joints
- D. None of the above
Explanation: ***Nerve supply of joints, muscles moving them, and overlying skin*** - **Hilton's law** states that the nerve supplying a joint also supplies the muscles that move the joint and the skin overlying the insertions of those muscles - This anatomical principle is clinically significant as it explains **referred pain patterns** from joints to surrounding structures - The law demonstrates the **functional integration** between joint innervation, muscle control, and cutaneous sensation *Nerve innervation only* - While Hilton's law involves nerve innervation, this option is too vague and incomplete - The law specifically describes the **relationship between three components**: joint nerves, muscle nerves, and cutaneous nerves - Simply stating "nerve innervation only" misses the **clinical significance** of the anatomical pattern *Blood supply to joints* - This refers to the vascular supply of joints (articular arteries), which is important for joint nutrition - However, **Hilton's law** specifically addresses **nerve supply patterns**, not vascular anatomy - Blood supply to joints follows different anatomical principles *None of the above* - This is incorrect because Hilton's law clearly relates to the integrated nerve supply pattern described in the correct option - The law is a fundamental principle in anatomy explaining the **functional relationship** between joint, muscle, and skin innervation
Question 6: A moving vehicle hits a pedestrian on his lateral aspect of the knee and causes a fracture. The fracture line is passing through the intercondylar eminence. Which of the following structures will most likely be injured
- A. Medial collateral ligament
- B. Medial meniscus
- C. Anterior cruciate ligament (Correct Answer)
- D. Lateral collateral ligament
Explanation: ***Anterior cruciate ligament*** - A fracture of the **intercondylar eminence** typically involves the avulsion of the **tibial attachment** of the anterior cruciate ligament (ACL). - The ACL's fibers attach to the **tibial intercondylar area**, making it highly susceptible to injury with a fracture in this region. *Medial collateral ligament* - The **medial collateral ligament** (MCL) originates from the medial femoral epicondyle and attaches to the medial tibia, primarily resisting valgus forces. - While knee trauma can affect the MCL, a fracture of the intercondylar eminence specifically points to an injury involving a structure attached to that area. *Medial meniscus* - The **medial meniscus** is a C-shaped cartilage in the knee joint and can be injured by rotational forces or compression. - Its injury is not directly linked to an intercondylar eminence fracture, although severe trauma can injure multiple structures. *Lateral collateral ligament* - The **lateral collateral ligament** (LCL) originates from the lateral femoral epicondyle and attaches to the fibular head, resisting varus forces. - An injury to the LCL is less likely with an intercondylar eminence fracture, as the LCL does not attach to this specific tibial region.
Question 7: The mechanoreceptors in joints and ligaments are:
- A. Adapt differentially for different stresses
- B. Slow adapting (Correct Answer)
- C. Fast adapting
- D. Non adapting
Explanation: ***Slow adapting*** - **Mechanoreceptors** in joints and ligaments, such as **Ruffini endings** and **Golgi-type endings**, are primarily **slowly adapting**. - This characteristic allows them to provide continuous information about **joint position** and **pressure** over extended periods. *Adapt differentially for different stresses* - While different mechanoreceptors respond to different types of stimuli (e.g., pressure, stretch), this option describes varying responses rather than the fundamental **adaptation rate**. - The primary characteristic being asked for is how their firing rate changes over time in response to a constant stimulus. *Fast adapting* - **Fast-adapting mechanoreceptors**, like **Pacinian corpuscles** and **Meissner's corpuscles**, respond strongly at the onset and offset of a stimulus. - They are more involved in sensing **vibration** and **changes in pressure** rather than sustained joint position. *Non adapting* - All biological sensory receptors exhibit some degree of **adaptation** to a constant stimulus, meaning their firing rate changes over time. - A truly **non-adapting** receptor would fire at a constant rate indefinitely for a given stimulus, which is not characteristic of mechanoreceptors.
Question 8: Which muscles are paralyzed if there is hyperextension of metacarpophalangeal joint and flexion of the interphalangeal joint?
- A. Extensor digitorum
- B. Adductor pollicis
- C. Pronator quadratus muscle
- D. Interossei and lumbricals (Correct Answer)
Explanation: ***Interossei and lumbricals*** - Paralysis of the **interossei** and **lumbricals** leads to an imbalance in muscle forces, causing the **extensor digitorum** to hyperextend the **metacarpophalangeal (MCP)** joints. Together with the interossei, these muscles normally bring about flexion of the MP joints and extension of the interphalangeal (IP) joints [1]. - The unopposed action of the **flexor digitorum profundus** and **superficialis** then causes flexion of the **proximal interphalangeal (PIP)** and **distal interphalangeal (DIP)** joints, resulting in a **claw hand** deformity. *Extensor digitorum* - Paralysis of the **extensor digitorum** would primarily result in an inability to extend the fingers, leading to a **flexed posture** rather than hyperextension of the MCP joints. - It would not cause the characteristic flexion of the interphalangeal joints seen in this condition. *Adductor pollicis* - Paralysis of the **adductor pollicis** would affect the thumb's ability to adduct, impacting pinch strength and grasp, but it does not directly cause the described finger deformity. - This muscle is primarily involved in thumb movement, not the general finger mechanics described. *Pronator quadratus muscle* - The **pronator quadratus muscle** is responsible for **pronation of the forearm**. - Its paralysis would affect forearm rotation at the wrist, but it has no direct role in the movement or posture of the metacarpophalangeal or interphalangeal joints.
Question 9: In Articular cartilage, most active chondrocytes are seen in ?
- A. Zone 1
- B. Zone 4
- C. Zone 3
- D. Zone 2 (Correct Answer)
Explanation: ***Zone 2*** - This is the **transitional (or middle) zone**, where chondrocytes are numerous and more metabolically active, responsible for synthesizing major components of the extracellular matrix. - Chondrocytes here are typically **ovoid or round**, arranged somewhat randomly, and are involved in maintaining the cartilage structure. *Zone 1* - This is the **superficial (or tangential) zone**, where chondrocytes are **flattened** and oriented parallel to the articular surface. - Their primary role is to resist shear forces, and they are generally less metabolically active compared to those in the transitional zone. *Zone 3* - This is the **deep (or radial) zone**, characterized by **columnar arrangements** of chondrocytes. [1] - While these chondrocytes are metabolically active and synthesize matrix components, they are generally less active than those in the transitional zone and are more involved in resisting compressive forces. *Zone 4* - This is the **calcified zone**, directly adjacent to subchondral bone, where chondrocytes are **sparse** and often hypertrophic prior to eventual calcification. - This zone acts as an interface between cartilage and bone, and its chondrocytes have significantly reduced metabolic activity once calcification occurs. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1184.
Question 10: A sportsman presented to you after injury during practice exercise. You performed the test given in the image, and it came out as positive. What is the diagnosis?
- A. Anterior cruciate ligament tear (Correct Answer)
- B. Posterior cruciate ligament tear
- C. Medial meniscus tear
- D. Medial collateral ligament tear
Explanation: ***Anterior cruciate ligament tear*** - The image depicts the **Lachman test**, a highly sensitive and specific clinical test for **ACL integrity**. - A positive Lachman test, characterized by *increased anterior tibial translation* and a *soft or absent endpoint*, confirms an **ACL tear**. *Posterior cruciate ligament tear* - A PCL tear is identified by tests like the **posterior drawer test** or **posterior sag sign**, which show *posterior tibial translation*. - The test shown in the image specifically assesses **anterior stability**, not posterior. *Medial meniscus tear* - Medial meniscus tears are typically diagnosed with tests like **McMurray's test** or **Apley's grind test**, which involve *rotation* and *compression* of the knee. - While a crucial knee structure, the meniscus does not primarily contribute to **anterior-posterior stability** in the way the ACL does. *Medial collateral ligament tear* - An MCL tear is detected by applying a **valgus stress** to the knee at various degrees of flexion. - This tear presents with *medial joint line pain* and *instability to valgus stress*, which is not assessed by the depicted test.
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